The preparation of highly conductive, high-surface-area, heteroatom-doped, porous carbon nanocomposite materials with enhanced electrochemical performance for sustainable energy-storage technologies, such as supercapacitors, is challenging. Herein, a route for the large-scale synthesis of nitrogen-doped porous carbon wrapped partially exfoliated carbon nanotubes (N-PPECNTs) with an interconnected hierarchical porous structure, as an advanced electrode material that can realize several potential applications for energy storage, is presented. Polypyrrole conductive polymer acts as both nitrogen and carbon sources that contribute to the pseudocapacitance. Partially exfoliated carbon nanotubes (PECNTs) provide a high specific surface area for ion and charge transportation and act as a conductive matrix. The derived porous N-PPECNT displays a nitrogen content of 6.95 at %, with a specific surface area of 2050 m g , and pore volume of 1.13 cm g . N-PPECNTs, as an electrode material for supercapacitors, exhibit an excellent specific capacitance of 781 F g at 2 A g , with a high cycling stability of 95.3 % over 10 000 cycles. Furthermore, the symmetric supercapacitor exhibits remarkable energy densities as high as 172.8, 62.7, and 53.55 Wh kg in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][TFSI]), organic, and aqueous electrolytes, respectively. Also, biocompatible hydrogel and polymer gel electrolyte based, stable, flexible supercapacitors with excellent electrochemical performance could be demonstrated.
The
scalable design and inexpensive synthesis of high-surface-area conductive
porous carbon
electrode materials for high-performance supercapacitors have found
extensive interest. Typically, the inherent structure and composition
of the biomass or biowaste influence the final structural and morphological
properties of carbon nanomaterials. To investigate the influence of
internal microstructure on the final products and their effect on
electrochemical performance, herein, for the first time, we demonstrated
a facile approach for the synthesis of three unique microstructures.
N-doped two-dimensional wrinkled few-layered porous graphene nanosheets
(N-HGNSs), three-dimensional honeycomb-like porous carbon (N-HPC),
and carbon microflakes (N-CMF) are synthesized from three different
parts of a single biowaste material, Bombax malabaricum. N-HGNS, N-HPC, and N-CMF electrode materials exhibit high specific
capacitance (C
p) values of 523, 458, and
363 F g–1, respectively, at a high current density
of 1.5 A g–1 in 1 M H2SO4 with
a high rate capability of ∼82% at 30 A g–1, which are, to the best of our knowledge, among the highest ever
testified for N-doped carbon materials obtained from biowaste. Furthermore,
a fully biocompatible flexible solid-state supercapacitor device is
successfully designed with high energy densities of 19.4 and 17.84
Wh kg–1, as well as excellent energy densities of
76.9 and 53 Wh kg–1 are presented in Na2SO4 electrolyte for N-HGNS and N-HPC electrodes, respectively.
It is believed that this single-step novel green approach could aid
in the design
of an efficient and large-scale process to prepare electrode materials
with tunable properties from biowaste for excellent energy storage
applications. Furthermore, the three flexible supercapacitors connected
in series can power
a red light-emitting diode for 20 and 15 min after charging for 60
s for N-HGNS and N-HPC, respectively.
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